Recently there has been significant focus on the preparation of various polymers from their oligomeric structures. Generally the oligomeric structures have better flow properties than the final polymer and therefore can be used to make various articles where the initial flow is a significant feature of the article, for example, in composite formation the flow of the oligomer is a significant feature in filling the mold and wetting the reinforcing material.
Attention has been focused on the use of cyclic carbonate oligomers for preparing polycarbonate. By using mixtures of cyclic carbonate oligomers, the softening point of the oligomers is of a sufficiently low temperature that various commercial uses of the cyclic carbonate oligomers are now possible. These uses particularly include the preparation of high molecular weight polycarbonate composite materials. These materials can be used in various applications wherein the general strength and toughness of the polycarbonate is added to by the reinforcing material so that an extremely high modulus is also achieved. The typical method of preparing the polycarbonate composite is to prepare the cyclic carbonate oligomers, add a polymerization catalyst system to the oligomers, add the oligomers to a specific reinforcing material, and raise the temperature to set off the polymerization catalyst system so as to form the high molecular weight polycarbonate resin composite.
This particular method, however, has some problems since the actual catalyst system can make the high molecular weight polymers in less than three minutes at 300.degree. C. Because of this rapid build up in molecular weight, it is considered quite difficult to mold large reinforced particles in an injection molding machine, pultrusion equipment or on the usual equipment used to mold thermoplastic composites due to the short polymerization time.
A new method has been discovered which increases the polymerization time and therefore allows the composite materials to be prepared in the usual commercial apparatuses. In this method the catalyst system is not dispersed within the cyclic carbonate oligomer but is impregnated upon the reinforcing material. This increases the amount of time necessary to bring about the actual polymerization of the oligomer to the high molecular weight polycarbonate. Interestingly, even though the catalyst system is not dispersed within the cyclic carbonate oligomer, the preparation of the high molecular weight polycarbonate is uniform or at least substantially uniform throughout the material, even at the edges of the molded article.